AbstractProgress in modern biology and particularly in neuroscience constantly relies on the development of new techniques to investigate the structural and dynamical complexity of living matter at the cellular and sub-cellular size levels. An ongoing challenge is to achieve minimally-invasive and high-resolution observations of neuronal activity in vivo inside deep brain areas. A perspective strategy is to utilise holographic control of light propagation in complex media, which allows converting a hair-thin multimode optical fibre into an ultra-narrow imaging tool. Compared to current endoscopes based on GRIN lenses or fibre bundles, this concept offers a footprint reduction exceeding an order of magnitude, together with a significant enhancement in resolution.
This thesis represents one of the first attempts to move multimode fibre based systems from imaging of static targets and fixed samples, towards dynamic and challenging environments as a living animal.
High-performance holographic methods implemented on the fastest available nowadays spatial light modulator allowed to design compact and high-speed system for raster-scan fluorescent imaging at the tip of a fibre with micron-scale resolution, dictated only by the numerical aperture of the probe and the high purity/contrast of the focal points approaching the theoretical limits. These factors made the system capable of in-vivo observations of cell bodies and processes of inhibitory neurons within deep layers of the visual cortex and hippocampus of anesthetised mice.
Future advancements will strongly rely on the development of new fibre types directly optimised for the purposes of holographic endoscopy. Utilising such custom-made fibre with significantly enhanced numerical aperture, allowed demonstration of the focusing power of the best water-immersion physiology objectives, but also extend the applicability of holographic endoscopy towards minimally-invasive implementation of optical manipulation.
The results achieved pave the way to in-vivo implementation of numerous techniques of modern microscopy including multiphoton, super-resolution and light-sheet approaches, which will build further on the performance presented here.
|Date of Award||2018|
|Supervisor||Kees Weijer (Supervisor) & Tomas Cizmar (Supervisor)|